1. Field of the Invention
The present invention is directed towards apparatus and methods for penetrating tissue and creating openings therein in order to provide access to the interior of a patient's body. The present invention provides apparatus and methods which are particularly suited for creating openings which provide access to anatomical cavities, either directly through the opening itself or through a cannula positioned within the tissue opening. One embodiment of the present invention comprises a trocar.
2. Description of Related Art
Various medical procedures require the penetration of tissue to provide access to the interior of the patient's body. This is particularly true, for example, of endoscopic procedures wherein an opening in tissue must first be created to provide access to anatomical cavities or other internal structures. As used herein, "endoscopic" refers to procedures which employ tubular optical instruments (i.e., endoscopes) which are inserted into a patient to provide vision therein. The endoscope also typically has a hollow cannula through which other instruments may be inserted into the patient. The term "endoscopic" is generic to, and therefore includes, terms such as "laparascopic" and "arthroscopic" which refer to the use of an endoscope in a particular region of the body. Typically, a cannula is positioned within the tissue opening, and various medical instruments (such as an endoscope) may then be passed through the cannula into the interior of the patient.
One commonly-employed instrument for penetrating tissue is referred to as a trocar, and generally comprises a cutting assembly (or obturator) and an outer cannula (also referred to as the trocar tube or sleeve). The cannula is positioned against the patient's skin, and the cutting assembly is positioned within the interior of the cannula. The sharp distal end of the cutting assembly is then urged through the skin until it enters the anatomical cavity being penetrated. The cannula is then urged through the tissue opening created by the cutting assembly, and the cutting assembly is thereafter withdrawn. The cannula remains in place, and provides a passageway through which access to the anatomical cavity is provided.
Urging the cutting assembly of a trocar, or, for that matter, any other sharp instrument, through tissue can be dangerous if not performed properly. Blood vessels, organs and other delicate structures within the patient's body can be inadvertently damaged by the cutting assembly. Even more problematic is the fact that such inadvertent damage can go initially undetected, thereby leading to further complications. In fact, injury to major blood vessels, particularly in the abdomen, has become more common as the use of endoscopes has increased. Unfortunately, such vascular injuries often prove fatal, particularly if they go undetected for a significant period of time.
Various techniques and apparatus have been developed in order to reduce the risk associated with trocars. For example, a hollow needle (commonly referred to as a Veres needle) may be inserted into the abdomen, and a gas introduced therethrough in order to insufflate the abdomen. Insufflation causes a tenting-up of the abdomen, which tends to reduce the potential for over-insertion of the cutting blade. Vascular damage can and still does occur, however, and improper insertion of the insufflation needle has even been known to cause serious injury or death.
Numerous types of "safety trocars" have also been developed, wherein a spring-loaded shield helps prevent inadvertent damage caused by the cutting tip. The shield retracts away from the tip as the cutting blade is urged through the tissue. Once the cutting blade has passed into the anatomical cavity and the tissue is no longer bearing against the shield, the shield springs forward to cover the cutting blade. Such trocars are described, for example, in U.S. Pat. Nos. 5,116,353, 5,215,526, and 5,707,362. Even such "safety trocars," however, are not foolproof, and trocar injuries and deaths have continued to rise even as the use of these safety trocars has become more widespread.
Unfortunately, more and more endoscopic surgical procedures are developed each year. For example, gallbladder removal (referred to as a cholecystectomy), which once required a large abdominal incision and several days of in-hospital recovery, may now be performed laparascopically through a small umbilical incision on an out-patient basis. Not surprisingly, patient demand for such procedures has also increased significantly, due to their minimally-invasive nature, reduced post-operative recovery time, and lower cost.
The development of improved endoscopes has also provided physicians with a minimally-invasive means for direct examination of the interior of a patient. The result is that many patients, particularly those suffering from certain forms of cancer, are subjected to multiple examinations and procedures by means of an endoscope. In fact, some cancer patients undergo multiple laparoscopic procedures over a short period of time. Unfortunately, the increased frequency of these procedures greatly increases the risk of injury or death associated with trocar insertion. Thus, there is a need for apparatus and methods which will decrease the possibility of inadvertent patient injury during tissue penetration, particularly during cannula insertion of endoscopic procedures.